Magnetic modulator systems are typically used to generate high peak power electrical pulses for a variety of applications. In its simplest form, a magnetic modulator system consists of two principal sections as illustrated in FIG. 1: the commutation circuit 2 and the magnetic pulse compression network 4. The commutation circuit 2, sometimes referred to as the intermediate energy storage (IES) circuit, transfers energy to the input of the magnetic pulse compression network 4. The magnetic pulse compression network 4 compresses the energy. As illustrated, the magnetic pulse compression network 4 consists of a number of shunt capacitor elements each separated by a saturable inductor, generally known to those in the art as a magnetic switch. Specifically, the commutation circuit 2 and the pulse compression network 4 operate in concert as follows.
A power supply unit 6 in the commutation circuit 2 charges an energy storage capacitor C.sub.0 8 to a specified voltage V.sub.0. Once charged, C.sub.0 8 is discharged through switch S.sub.1 10 and inductor L.sub.0 22, into the input of the magnetic pulse compression network 4. This is indicated by the current waveform i.sub.o (t) shown in FIG. 2.
The discharge of C.sub.0 8 into the magnetic pulse compression network 4 causes the energy, originally stored in C.sub.0 8 to be resonantly transferred to capacitor C.sub.1 12 over a period t.sub.0. As a result, C.sub.1 12 charges to a voltage determined by the turns ratio of transformer T.sub.1 14.
While C.sub.1 12 is being charged, magnetic switch (MS.sub.1) 16 is initially biased such that it presents a high impedance to the voltage across the switch. As a result, while C.sub.1 12 is being charged, little current flows through MS.sub.1 16. MS.sub.1 16 is designed such that when C.sub.1 12 is fully charged, MS.sub.1 16 saturates meaning that the impedance of MS.sub.1 16 significantly decreases allowing the discharge of C.sub.1 12 into C.sub.2. Temporal compression of the energy pulse is achieved by designing the network such that each capacitor is discharged significantly faster than it was charged. By cascading a number of magnetic pulse compression stages, an energy pulse can be compressed temporally to very short pulse widths, thereby achieving large peak powers at the output of the magnetic pulse compression network 4.
The temporal compression which is achieved as the energy pulse propagates through the magnetic pulse compression network 4 is illustrated in FIG. 2. Capacitor C.sub.1 12 is discharged through MS.sub.1 16 over the period t.sub.1 as indicated. The subsequent discharge of C.sub.2 through MS.sub.2 occurs over a period t.sub.2, where t.sub.2 is shorter than t.sub.1. This process continues until the last capacitor C.sub.n is discharged through MS.sub.n into the load 20 over a period t.sub.n.
Under ideal conditions, the impedance of the load 20 is matched to that of the output stage of the magnetic pulse compression network 4. Under such circumstances, all of the energy will be coupled to the load 20 and dissipated. Therefore, no energy will be reflected from the load 20 back into the output of the magnetic pulse compression network 4. However, in a number of applications, it is impractical, if not impossible, to ensure that the load impedance is always matched to that of the output stage of the compression network 4. As a result, a fraction of the energy arriving at the output of the magnetic pulse compression network 4 may be reflected towards the front end of the network. In general, the greater the impedance mismatch between the output of the network and the load 20, the greater the magnitude of the reflected energy.
Uncontrolled energy reflections in the form of reversed voltages can be a serious problem for the modulator system. This is because the circuit dynamics of the magnetic pulse compression network 4 are such that negative voltage reflections will be quickly propagated towards the front end of the network, relatively unimpeded by the network itself. As a result, it is possible to obtain very large reflections at the input of the magnetic pulse compression network 4 in the form of reversed voltages. If not properly handled, the reflected energy may be transferred back to the commutation circuit 2 in the form of voltage reversals on C.sub.0 8. This may cause significant damage to portions of the commutation circuit 2. In particular, if the power supply unit 6 is of the switch-mode capacitor charging type, a high level of voltage reversal on C.sub.o 8 can cause damage to the power supply unit 6. In addition, the reflected energy may continue to be transferred back and forth between the commutation circuit 2 and the magnetic pulse compression network 4, possibly causing damage to the modulator system or interfering with its desired operation on subsequent pulses.